GPUImage pencil sketch filter optimisation - image-processing

Question

I have implemented pencil sketch filter using GPUImage framework. But I think the filter is too much complex to produce the output.
Pencil Filter function
- (void)pencilSketch
{
//UIImage *inputImage = [UIImage imageNamed:#"portrait.jpg"];
UIImage *inputImage = [UIImage imageNamed:#"selfie4.jpg"];
GPUImageGrayscaleFilter *grayFilter = [[GPUImageGrayscaleFilter alloc] init];
GPUImageColorInvertFilter *edgeFilter = [[GPUImageColorInvertFilter alloc] init];
GPUImageGaussianBlurFilter *blurr = [[GPUImageGaussianBlurFilter alloc] init];
blurr.blurRadiusInPixels = 8.0; // Edge Sensitivity
blurr.texelSpacingMultiplier = 8.0; // Edge Strength
GPUImageLinearBurnBlendFilter *filter = [[GPUImageLinearBurnBlendFilter alloc] init];
UIImage *invImg = [edgeFilter imageByFilteringImage: inputImage]; // Color Invert
UIImage *blurrImg = [blurr imageByFilteringImage: inputImage]; // Gaussian Blurr
// Linear Burn Blend
GPUImagePicture *mainPicture = [[GPUImagePicture alloc] initWithImage: invImg];
GPUImagePicture *topPicture = [[GPUImagePicture alloc] initWithImage: blurrImg];
[mainPicture addTarget: filter];
[topPicture addTarget: filter];
[filter useNextFrameForImageCapture];
[mainPicture processImage];
[topPicture processImage];
UIImage *resultedimage = [filter imageFromCurrentFramebuffer];
resultedimage = [UIImage imageWithCGImage:[resultedimage CGImage] scale:1.0 orientation: invImg.imageOrientation];
GPUImageColorInvertFilter *bf = [[GPUImageColorInvertFilter alloc] init];
resultedimage = [bf imageByFilteringImage: resultedimage]; // Color Invert
resultedimage = [grayFilter imageByFilteringImage: resultedimage]; // Gray scale
UIImage *grainImage = [UIImage imageNamed:#"stroke2.jpg"];
GPUImageGaussianBlurFilter *gBlurr = [[GPUImageGaussianBlurFilter alloc] init];
gBlurr.blurRadiusInPixels = 5.0;
UIImage *blurrGrainImg = [gBlurr imageByFilteringImage: grainImage];
GPUImagePicture *blurrPic = [[GPUImagePicture alloc] initWithImage: resultedimage];
GPUImagePicture *topPic = [[GPUImagePicture alloc] initWithImage: blurrGrainImg];
GPUImageSoftLightBlendFilter *maskedFilter = [[GPUImageSoftLightBlendFilter alloc] init];
[blurrPic addTarget: maskedFilter];
[topPic addTarget: maskedFilter];
[maskedFilter useNextFrameForImageCapture];
[blurrPic processImage];
[topPic processImage];
resultedimage = [maskedFilter imageFromCurrentFramebuffer];
resultedimage = [UIImage imageWithCGImage:[resultedimage CGImage] scale:1.0 orientation: inputImage.imageOrientation];
GPUImageColorBurnFilter *bFilter = [[GPUImageColorBurnFilter alloc] init];
bFilter.brightness = 5.0; // Edge Darkness
resultedimage = [bFilter imageByFilteringImage: resultedimage];
baseImage.image = resultedimage;
}
Output image for as result of the filter
Please anyone suggest me how to optimise this filter?
I would like if anyone guide me to write shader program for this. I can make a custom GPUImageFilter and write shader program for the same.

Answer 1

UIImage *imgCropped=image;
stillImageSource = [[GPUImagePicture alloc] initWithImage:imgCropped];
saturationFilter=[[GPUImageSaturationFilter alloc]init];
[saturationFilter setSaturation:0];
[stillImageSource addTarget:saturationFilter];
[stillImageSource processImage];
[saturationFilter useNextFrameForImageCapture];
UIImage *copyImage=[saturationFilter imageFromCurrentFramebuffer];
stillImageSource=[[GPUImagePicture alloc] initWithImage:copyImage];
copyGPUimage=[[GPUImagePicture alloc] initWithImage:copyImage];
invertFilter=[[GPUImageColorInvertFilter alloc]init];
[ copyGPUimage addTarget:invertFilter];
[ copyGPUimage processImage];
[invertFilter useNextFrameForImageCapture];
UIImage *imgTempr=[invertFilter imageFromCurrentFramebuffer];
copyGPUimage= [[GPUImagePicture alloc]initWithImage:imgTempr];
gaussianBlur=[[GPUImageGaussianBlurFilter alloc]init];
[gaussianBlur setBlurRadiusInPixels:val];
[copyGPUimage addTarget:gaussianBlur];
[ copyGPUimage processImage];
[gaussianBlur useNextFrameForImageCapture];
UIImage *imgTempa=[gaussianBlur imageFromCurrentFramebuffer];
copyGPUimage= [[GPUImagePicture alloc]initWithImage:imgTempa];
colorDodge=[[GPUImageColorDodgeBlendFilter alloc]init];
[stillImageSource addTarget:colorDodge];
[ copyGPUimage addTarget:colorDodge];
[stillImageSource processImage];
[ copyGPUimage processImage];
[colorDodge useNextFrameForImageCapture];
imageWithAppliedThreshold=[colorDodge imageFromCurrentFramebuffer];
//here you have got your sketch now you can set its darkness
stillImageSource = [[GPUImagePicture alloc] initWithImage:imageWithAppliedThreshold];
monochromeFilter=[[GPUImageMonochromeFilter alloc]init];
[monochromeFilter setIntensity:intenVal];
[monochromeFilter setColorRed:0.0 green:0.0 blue:0.0];
[monochromeFilter setBackgroundColorRed:1.0 green:1.0 blue:1.0 alpha:1.0];
[stillImageSource addTarget: monochromeFilter];
[stillImageSource processImage];
[monochromeFilter useNextFrameForImageCapture];
imageWithAppliedThreshold=[monochromeFilter imageFromCurrentFramebuffer];